Blue Sea 7317-BSS 50A Double Pole Toggle Breaker

The Blue Sea Systems 7317-BSS is a 50-amp double pole circuit breaker built around a magnetic hydraulic trip mechanism. It's rated for 277 volts AC and 65 volts DC, wears a simple toggle actuator, and belongs to Blue Sea's A-Series. This is the breaker you reach for when you want dependable overcurrent protection that doesn't care how hot your electrical panel gets.

Here's why the magnetic hydraulic part matters. This breaker trips on the actual current flowing through it, not on the temperature around it. A thermal breaker tucked next to a warm engine or baking in a sun-soaked helm can nuisance-trip, or worse, trip late when you actually need it. This one holds its rated 50 amps whether it's a cold morning at the dock or a hundred-degree afternoon in the engine space. When a genuine fault shows up, it opens cleanly. That consistency is the whole point.

Being double pole, it breaks both conductors at the same time. That's exactly what you want on 240-volt split-phase shore power, or on any larger AC circuit where both legs need to open together. The 277-volt AC rating covers standard marine shore-power voltages with plenty of headroom. And the 65-volt DC rating means it isn't just an AC part. It'll protect higher-voltage DC systems too, including 48-volt lithium banks that are showing up on more and more boats.

The "For Use When Military Specifications Are Under CFR 46" line on this part isn't marketing fluff. CFR 46 is the U.S. federal code that governs commercial shipping and inspected vessels. If you're wiring a boat that has to meet those standards, this breaker is built to qualify. And if you're a recreational boater, you still get that same build quality in your panel. No downside.

Wiring it in is straightforward. The #10-32 screw terminals take ring lugs on 8 to 10 AWG wire, which lines up right with a 50-amp circuit. Snug the screws down firmly, but don't lean on them. Over-torquing a breaker terminal can crack the base, and on a boat that's the kind of intermittent failure you'll chase for a whole season. Do it once, do it right.

One thing to measure before you buy: the depth behind your panel. Magnetic hydraulic breakers sit a little deeper than basic thermal units, so if you're swapping one into a tight console, confirm you've got the clearance first. It's a two-minute check that saves a headache.

This is a single-unit breaker, so you install it as an individual component rather than as part of a pre-built panel assembly. It's a natural fit feeding a 50-amp inverter or charger, or a heavy AC branch off a Blue Sea AC panel. Where you can, keep your magnetic hydraulic and thermal breakers on separate buses so the whole system behaves predictably and you always know what you're looking at.

There's a practical bonus to the toggle actuator, too. It doubles as a manual switch. You can flip the circuit off right at the panel when you're working on a load downstream, then flip it back on when you're done, no separate switch needed. On a boat where panel real estate is tight, folding the switch and the breaker into one device is a small thing that adds up fast.

Blue Sea Systems builds this part for the marine environment, where salt, vibration, and heat wear down lesser hardware in a hurry. The A-Series is their bread-and-butter breaker line for exactly that reason, engineered to hold up in the conditions boats actually live in. It's the sort of component you wire in once and forget about, which is honestly the highest compliment you can pay a circuit breaker.

And if you're running it on 240-volt split-phase, both poles carry a leg and open together the instant something goes wrong. Wire it per standard AC practice and it'll sit quietly in the panel for years, doing exactly one job: cutting the circuit the moment there's a fault. That's all you want from a breaker, and it's what this one delivers.